Mole

Someone at the textbook publishing company really said "yeah, let's illustrate molarity with two literal rodents crammed into a beaker" and nobody stopped them. I've been teaching chemistry for years and I'm still not over how beautifully cursed this is.

For those blissfully unaware: a mole in chemistry is Avogadro's number (6.02 × 10²³) of particles—you know, the unit that makes stoichiometry possible. But these textbook designers took the homophone route and gave us two actual moles (the animals) stuffed in a graduated cylinder to represent "two moles per litre." It's technically educational and simultaneously the most unhinged diagram you'll find in a legitimate science textbook.

The poor creatures look absolutely done with this situation, which is exactly how students feel when calculating limiting reagents at 2 AM. Educational? Debatable. Memorable? Absolutely. Will I ever unsee this? Never.